JNK is required for maintaining the tumor-initiating cell-like properties of acquired chemoresistant human cancer cells

Aim: Many studies reveal an association between the acquired chemoresistant phenotype of cancer cells and tumor-initiating cell-like properties. The aim of this study was to determine the impact of c-Jun N-terminal kinase (JNK) on the tumor-initiating cell-like properties of acquired chemoresistant human cancer cells. Methods: Two well-established human acquired chemoresistant cancer cell lines K562/A02 and KB/VCR, as well as their respective parental counterparts K562 and KB were tested. The expression of relevant mRNAs and proteins was detected using qRT-PCR and Western blotting, respectively. Sphere formation and self-renewal assays were used to study the tumor-initiating cell-like properties. Soft agar and colony formation assays were used to investigate tumorigenic ability. Results: We observed that suppressing JNK activity by its specific small molecule inhibitor SP600125 or by limiting JNK1/2 expression with JNK1/2 shRNA lentiviruses inhibited the expression of pluripotent stem cell markers such as Oct4, Sox2, and Nanog in KB/VCR cells and K562/A02 cells as well as sphere formation and self-renewal abilities of K562/A02 cells. Additionally, inhibition of JNK activity significantly inhibited the in vitro and in vivo tumor-initiating abilities of KB/VCR cells. Furthermore, our data suggest that blocking JNK activity abundantly inhibited the Hedgehog (Hh) pathway activity, as reflected by reduction of Hedgehog (Hh) pathway target genes Gli1 and ptch1 at the mRNA level as well as Gli-luciferase activity. Conclusion: JNK maintains the tumor-initiating cell-like properties of acquired chemoresistant K562/A02 and KB/VCR cells potentially through activating the Hedgehog pathway. Thus, disruption of tumor-initiating cell-like properties by targeting JNK may be a new approach to combating acquired chemoresistance.